This invention relates to apparatus for controlling the flow of production fluid into a well flow conductor or tubing string, from the annulus surrounding that tubing string, and more particularly to side pocket mandrels and flow control devices contained in the side pocket receptacle thereof for that purpose.
Side pocket mandrels have been used for many years for different applications involving the flow of fluid from the exterior of a tubing string into the interior thereof. Davis et al U.S. Pat. No. 4,066,128, issued Jan. 3, 1978, is concerned with a side pocket mandrel including a flow control device in the side pocket thereof for controlling the injection of gas into the tubing for a gas lift operation. The flow control device of this patent includes a sliding sleeve valve which controls the port opening into the side pocket receptacle from the exterior of the mandrel, and is shiftable between a port-closing and a port-opening position. This sliding sleeve valve is operated automatically by a flow control valve which is inserted selectively into the side pocket receptacle of the mandrel. When the control valve is placed therein, the sleeve valve is automatically moved to the port-opening position, and when the control valve is removed from the receptacle the sliding sleeve valve is moved to the port-closing position.
A valve for controlling the flow of production fluid into the tubing string must be a more rugged valve to withstand the abrasive characteristics of the production fluid, and desirably has the largest possible flow path to present minimal restriction to the flow of production fluid.
Prior art devices for this purpose include sliding sleeve valves, sometimes referred to as sliding side door valves, which are placed concentrically in the tubing string as components thereof and which function in a similar manner to the above mentioned sliding sleeve valve in that a sleeve is shiftable between a port-opening and port-closing condition. These valves are operated in a similar manner by the placing or removal of a flow control valve referred to as a standing valve, the sleeve valve being automatically shifted to the open condition when the standing valve is placed, and being shifted to the closing position when the standing valve is removed. A disadvantage of this arrangement is that if it is desired to perform any service work below the zone being produced, at least one trip must be made to remove the standing valve and shift the associated sleeve valve closed, thus shutting off production flow before the servicing work can be performed. The production flow of the well must remain shut off during any service work to be performed below that zone which is being produced. For a pumpdown installation, it may well be that production flow will have to be shut off for service work above that producing zone also, lest circulation be lost to the open zone.
Another prior art device for this purpose consists of a side pocket mandrel designed to receive a flow control valve in the side pocket receptacle. This type device has the advantage that the standing flow control valve is offset from the main flow path of the tubing string, and permits the passing of other well tools through the string past the standing valve for such service operations as may be required. A disadvantage of this device is that when the standing valve is removed, there is an open path between the exterior and interior of the tubing; and to close this path it is necessary to place in the side pocket receptacle a dummy choke valve. Two separate operations, then, are necessary to switch between an open flow condition and a no-flow condition. When using wireline servicing, two trips are usually required.
While the tools discussed above may be used for both wireline servicing and pumpdown servicing, it is more important in pumpdown servicing that tools may be designed to minimize the number of trips into the well since these trips are over a much longer distance than similar trips in wireline servicing. The demand for pumpdown servicing is increasing, and there are situations, such as a plurality of satellite wells serviced from a central platform, where pumpdown servicing is the only practical servicing method.
It is desirable then to provide a flow control device having the capability to control the flow of production fluid into the tubing string and including a combination sliding sleeve valve operated by a standing flow control valve to simplify the operations of placing and removing the standing flow control valve.